Saving configuration in modern Drupal

This is $form_state->getValues() flat (#tree set to FALSE):

  link_all: 0
  article_field_categories: 0
  article_field_tags: 0
  bond_disclosure_report_field_bond_disclosure_type: 0
  committee_meeting_field_committee: 0
  committee_meeting_document_field_committee: 0
  committee_meeting_document_field_meeting_doc_type: 0
  event_field_categories: 0
  page_field_page_type: 1
  press_release_field_categories: 0
  submit: 'Save configuration'
  form_build_id: form-8DvlpJLttFXCx64DCUdOn0vPycCiiKyIdNJbCGPCx44
  form_token: hX8vPQFxTqqp4Xm6Jds7Yug4VA1Vob11FjmIcXo-yaE
  form_id: createcontentwithcategory_settings
  op: 'Save configuration'
link_all: 0
target_nodes_fields:
  article:
    article_field_categories: 0
    article_field_tags: 0
  bond_disclosure_report:
    bond_disclosure_report_field_bond_disclosure_type: 0
  committee_meeting:
    committee_meeting_field_committee: 0
  committee_meeting_document:
    committee_meeting_document_field_committee: 0
    committee_meeting_document_field_meeting_doc_type: 0
  event:
    event_field_categories: 0
  page:
    page_field_page_type: 1
  press_release:
    press_release_field_categories: 0
submit: 'Save configuration'
form_build_id: form-BkNPXcaxiQ4i0cURKxcshqy9-CMmD_Gd-yx8vTNWMKU
form_token: hX8vPQFxTqqp4Xm6Jds7Yug4VA1Vob11FjmIcXo-yaE
form_id: createcontentwithcategory_settings
op: 'Save configuration'